)Institute of Crystallography RAS, Moscow, 117333, Russia.
)HREM was used to discover nanotubes (NTs) and to characterize NTs main types. At present time HREM is gradually moved to more complicated structure investigations including nanocrystal/ nanotube composites, fulleren peapods, ets. Recently a detailed simultaneous characterization of SWNTs with encapsulated nanocrystals was demonstrated using computer image restoration [1]. It turned out that HREM is effective in NTs (and composites) formation mechanism investigation.
Double-walled nanotubes (DWNTs) were obtained by the arc discharge technique in Ar+H2 atmosphere. HREM revealed outer diameter 1.9-5 nm and interlayer distance 0.4 nm [2]
Multilayered surface modulated nanotubes with fluctuating diameters caused by periodically interrupted movement of catalytic particles (CP) were fabricated by carbon evaporation at high gas pressure (Ar +N2, 1300 atm). Walls in this tubes were formed by continues graphene [3].
HREM of NTs (nanofibres) obtain by CVD revealed different types of conical graphene layers structures (CLNTs). Heat treatment resulted in structural modification (loops between open neighboring edges are formed) [4]. Micro – and nanotubes synthesized by PE-CVD revealed defected version of CLNTs. Tubes with straight and helical inner channels were observed. CPs are Ni single crystals and accumulating C facets are {100} and {110}, emitting facets are vicinal or non-singular and they are governing structure of the tubes [5]. This work was supported by ISTC Project No 1024
